In a computer system handling large-scale data, data is stored in a large-capacity storage device other than a host system. When an existing storage subsystem is replaced with a new storage subsystem in the computer system thereof, it is necessary to migrate data stored in the existing storage subsystem to the new storage subsystem in order to continuously use the data stored in the existing storage subsystem.
As one of subjects for migrating data when replacing the storage subsystems thereof, there is a problem regarding an increase in the burden of changing the settings of a host computer. Since each storage subsystem has its unique identifier, replacement of the storage subsystem causes a change of a data transmission and/or reception (I/O access) path from the host computer to a storage area (Logical Unit, hereinafter abbreviated as LU) of the storage subsystem. Therefore, a system administrator needs to change the settings of the host computer when replacing the storage subsystem. Patent Literature 1 discloses a method for reducing the burden of changing the settings of a host computer during data migration between a source storage subsystem and a target storage subsystem.
In Patent Literature 1 the source and target storage subsystems assigns, in addition to a port identifier specific to each system, a virtual port ID used to identify an access path from the host computer (hereinafter referred to the virtual port ID) to a port which serves as an access path from the host computer to the storage area above. With this method, the storage area of the target storage subsystem inherits and uses the virtual port ID of a logical unit of the source storage subsystem by procedures described below. As a result, the host computer can change an access target storage subsystem to the target storage subsystem by continuing I/O access to the above-mentioned storage area via the virtual port ID which is conventionally set. Such procedures are exemplified as follows.
Step 1: Data is copied from a storage area of the source storage subsystem to a storage area of the target storage subsystem.
Step 2: When a mirror state is established in Step 1, the host computer stops issuing I/O.
Step 3: A port of the target storage subsystem takes over a virtual port ID of a port of the source storage subsystem.
Step 4: The storage area of the target storage subsystem takes over an identifier of the storage area of the source storage subsystem.
Step 5: The host computer resumes issuing I/O.
With a conventional storage system, a host computer issues a write command to one storage device and stores data in a volume of the one storage device (hereinafter referred to as the primary storage device); and in synchronization with this storage processing, the host computer stores copy data of the above-mentioned data in a volume of the other storage device (hereinafter referred to as the secondary storage device). If a failure occurs in the primary storage device of the conventional storage system having such a redundant configuration, the processing is continued by using the copy data in the secondary storage device (see Patent Literature 1). If such Patent Literature 1 is used when the system administrator replaces the storage subsystem, the burden is reduced for the host computer to change the settings for accessing the storage area.